While copper or a copper alloy having excellent electrical conductivity have been used for electrical contact parts in the past, contact characteristics have been improved lately. Accordingly, usage of uncovered copper or copper alloy decreases, and products with various surface coatings applied on copper or a copper alloy increases. In particular, electrical contact materials with a noble metal coating applied on an electrical contact part are often used. Since Au, Ag, Pd, Pt, Ir, Rh, Ru and the like among the noble metals have stability and excellent electrical conductivity, they are used as various electrical contact materials. In particular, Ag has the most excellent electrical conductivity among metals and is relatively inexpensive among the noble metals. Accordingly, Ag is used in various fields.
Recently, electrical contact materials having excellent abrasion resistance are used for electrical contact materials associated with repetitive plugging and sliding such as a connector terminal and a sliding switch of an automobile harness, a contact switch mounted in a cellular phone, and terminals of a memory card. In general, contact materials using hard Ag and hard Au are used for improving abrasion resistance. A hard bright Ag plating material and others have been developed lately and are used for parts requiring various abrasion resistance since Ag is inexpensive as compared to Au, Pd and others. Still more, plating and cladding materials in which micro-particles are dispersed are also developed, and various materials in terms of sliding characteristics are developed for coating electrical contact materials.
Still more, there exist materials in which sealing or lubricant process is applied on a surface of the material after plating in order to improve sliding characteristics of the surface. For example, in Patent Document 1, pure Ag plating is applied, and an organic coating film formed of an aliphatic amine, mercaptan, or a mixture thereof is formed on the Ag plating to improve sulfuration resistance and abrasion resistance (see Japanese Patent Application No. H06-212491).